Screw Compressor for a Utility Vehicle

ABSTRACT

A screw compressor for a utility vehicle has a rotor housing, in which screw rotors of the screw compressor are arranged, a housing cover, and an air outlet pipe arranged on an output side of the housing cover and having a riser. The air outlet pipe has at least one oil separator.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a screw compressor for a utilityvehicle.

Screw compressors for utility vehicles are already known from the priorart. Such screw compressors are used to provide the compressed airrequired for the brake system of the utility vehicle, for example.

In this context, in particular oil-filled compressors, in particularalso screw compressors, are known, in the case of which it is necessaryto regulate the oil temperature. This is generally realized by virtue ofan external oil cooler being provided which is connected to theoil-filled compressor and to the oil circuit via a thermostat valve.Here, the oil cooler is a heat exchanger which has two mutually separatecircuits, wherein the first circuit is provided for the hot liquid, thatis to say the compressor oil, and the second circuit is provided for thecooling liquid. As cooling liquid, use may for example be made of air,water mixtures with an antifreeze, or another oil.

This oil cooler must then be connected to the compressor oil circuit bymeans of pipes or hoses, and the oil circuit must be safeguarded againstleakage.

This external volume must furthermore be filled with oil, such that thetotal quantity of oil is also increased. The system inertia is thusincreased. Furthermore, the oil cooler must be mechanically accommodatedand fastened, either by means of brackets situated in the surroundingsor by means of a separate bracket, which necessitates additionalfastening means and also structural space.

U.S. Pat. No. 4,780,061 has already disclosed a screw compressor with anintegrated oil cooling arrangement.

Furthermore, DE 37 17 493 A1 discloses a screw compressor installationwhich is arranged in a compact housing and which has an oil cooler onthe electric motor of the screw compressor.

A generic screw compressor is already known for example from DE 10 2004060 417 B4.

It is therefore the object of the present invention to advantageouslyfurther develop a screw compressor for a utility vehicle of the typementioned in the introduction, in particular such that an initial oilseparation can take place already before the fluid, in particular air,compressed by the screw compressor reaches the oil separator.

This object is achieved according to the invention by a screw compressorfor a utility vehicle equipped with a rotor housing in which the screwsof the screw compressor are arranged. An air outlet pipe is arranged atthe outlet side of the housing cover and has a riser line, wherein theair outlet pipe has at least one oil separator.

The invention is based on the underlying concept, in the case of a screwcompressor, of performing an initial oil separation already at theoutlet side of the housing cover and of the screws which serve for thecompression for example of the air or of some other fluid. This initialoil separation is realized not by way of a conventional oil separatorbut rather already by way of the air outlet pipe through which thecompressed fluid, in particular the compressed air, is discharged out ofthe rotor housing or, after the compression by the screws, onward in thescrew compressor.

By means of this oil separation that takes place already in the airoutlet pipe, it is made possible for the efficiency of the oilseparation to be considerably improved. In this way, it is also achievedthat the oil separator may possibly be dimensioned and configureddifferently, because an initial oil separation takes place alreadyupstream thereof.

Provision may furthermore be made for the oil separator means to have anoil return opening. Such an oil return opening may for example be anopening in a wall of the air outlet pipe, through which opening the oilthat precipitates on the walls of the air outlet pipe can run out.

In particular, provision may be made for the oil return opening toconnect the interior of the air outlet pipe to the oil sump. By means ofthis alone, a simple return of oil is achieved.

Provision may furthermore be made for the air outlet pipe to have anattachment piece by means of which the air outlet pipe is connected tothe housing cover, wherein the oil return opening is arranged in theregion of the attachment piece or adjacent to the attachment piece. Itis thus made possible for the oil return opening to be arranged so as torelatively directly follow the outlet of the housing cover, that is tosay at the location adjoined by the air outlet pipe. Any oil that hasalready precipitated there can thus be directly discharged out of theair outlet pipe.

The oil return opening may be formed by a simple bore. This permitssimple assembly and at the same time also simple positioning of the oilreturn opening.

Provision may furthermore be made for the air outlet pipe to be at leastpartially of conical form. By means of a conical form of the air outletpipe, it is made possible for oil particles to be separated out of theair, and for these to be prevented from exiting the air outlet pipe,owing to the action of gravitational force.

In particular, provision may be made for the riser line to be of conicalform at an end side. By means of such a conical widening of the riserline, it is made possible for the effect of separating oil particles anddroplets out of the air under the action of gravitational force to beimproved. The oil particles separated out in this way fall back into theair outlet pipe and collect in the region adjacent to the attachmentpiece of the air outlet pipe, and there, can flow via the oil returnopening back into the oil sump.

Further details and advantages of the invention will now be discussed inmore detail on the basis of an exemplary embodiment illustrated in thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional drawing through a screw compressoraccording to the invention;

FIG. 2 shows a perspective detail view of the rotor housing of the screwcompressor, with air outlet pipe of the screw compressor, as per FIG. 1,and

FIG. 3 shows a perspective sectional drawing through the air outlet pipeas per FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, in a schematic sectional illustration, a screw compressor10 in the context of an exemplary embodiment of the present invention.

The screw compressor 10 has a fastening flange 12 for the mechanicalfastening of the screw compressor 10 to an electric motor (not shown inany more detail here).

What is shown, however, is the input shaft 14, by which the torque fromthe electric motor is transmitted to one of the two screws 16 and 18,specifically the screw 16.

The screw 18 meshes with the screw 16 and is driven by means of thelatter.

The screw compressor 10 has a housing 20 in which the main components ofthe screw compressor 10 are accommodated.

The housing 20 is filled with oil 22.

At the air inlet side, an inlet connector 24 is provided on the housing20 of the screw compressor 10. The inlet connector 24 is in this casedesigned such that an air filter 26 is arranged at said inlet connector.Furthermore, an air inlet 28 is provided radially on the air inletconnector 24.

In the region between the inlet connector 24 and the point at which theinlet connector 24 joins to the housing 20, there is provided aspring-loaded valve insert 30, which is designed here as an axial seal.

This valve insert 30 serves as a check valve.

Downstream of the valve insert 30, there is provided an air feed channel32 which feeds the air to the two screws 16, 18.

At the outlet side of the two screws 16, 18, there is provided an airoutlet pipe 34 with a riser line 36.

In the region of the end of the riser line 36, there is provided atemperature sensor 38 by means of which the oil temperature can bemonitored.

Also provided in the air outlet region is a holder 40 for an airdeoiling element 42.

In the assembled state, the holder 40 for the air deoiling element hasthe air deoiling element 42 in the region facing toward the base (asalso shown in FIG. 1).

Also provided, in the interior of the air deoiling element 42, is acorresponding filter screen or known filter and oil separation devices44, which will not be specified in any more detail.

In the central upper region in relation to the assembled andoperationally ready state (that is to say as shown in FIG. 1), theholder for the air deoiling element 42 has an air outlet opening 46which leads to a check valve 48 and a minimum pressure valve 50. Thecheck valve 48 and the minimum pressure valve 50 may also be formed inone common combined valve.

The air outlet 51 is provided downstream of the check valve 48.

The air outlet 51 is generally connected to correspondingly knowncompressed-air consumers.

In order for the oil 22 that is situated and separated off in the airdeoiling element 42 to be returned again into the housing 20, a riserline 52 is provided which has a filter and check valve 54 at the outletof the holder 40 for the air deoiling element 42 at the transition intothe housing 20.

A nozzle 56 is provided, downstream of the filter and check valve 54, ina housing bore. The oil return line 58 leads back into approximately thecentral region of the screw 16 or of the screw 18 in order to feed oil22 thereto again.

An oil drain screw 59 is provided in the base region, in the assembledstate, of the housing 20. By means of the oil drain screw 59, acorresponding oil outflow opening can be opened, via which the oil 22can be drained.

Also provided in the lower region of the housing 20 is the attachmentpiece 60 to which the oil filter 62 is fastened. Via an oil filter inletchannel 64, which is arranged in the housing 20, the oil 22 is conductedfirstly to a thermostat valve 66.

Instead of the thermostat valve 66, it is possible for an open-loopand/or closed-loop control device to be provided by means of which theoil temperature of the oil 22 situated in the housing 20 can bemonitored and set to a setpoint value.

Downstream of the thermostat valve 66, there is then the oil inlet ofthe oil filter 62, which, via a central return line 68, conducts the oil22 back to the screw 18 or to the screw 16 again, and also to theoil-lubricated bearing 70 of the shaft 14. Also provided in the regionof the bearing 70 is a nozzle 72, which is provided in the housing 20 inconjunction with the return line 68.

The cooler 74 is connected to the attachment piece 60, as will bediscussed in more detail below in FIGS. 2 to 4.

In the upper region of the housing 20 (in relation to the assembledstate), there is situated a safety valve 76, by means of which anexcessively high pressure in the housing 20 can be dissipated.

Upstream of the minimum pressure valve 50, there is situated a bypassline 78, which leads to a relief valve 80. Via said relief valve 80,which is activated by means of a connection to the air feed 32, air canbe returned into the region of the air inlet 28. In this region, theremay be provided a ventilation valve (not shown in any more detail) andalso a nozzle (diameter constriction of the feeding line).

Furthermore, approximately at the level of the line 34, an oil levelsensor 82 may be provided in the outer wall of the housing 20. Said oillevel sensor 82 may for example be an optical sensor, and may bedesigned and configured such that, on the basis of the sensor signal, itcan be identified whether the oil level during operation is above theoil level sensor 82 or whether the oil level sensor 82 is exposed, andthus the oil level has correspondingly fallen.

In conjunction with this monitoring, it is also possible for an alarmunit to be provided which outputs or transmits a corresponding errormessage or warning message to the user of the system.

The function of the screw compressor 10 shown in FIG. 1 is as follows.

Air is fed via the air inlet 28 and passes via the check valve 30 to thescrews 16, 18, where the air is compressed. The compressed air-oilmixture, which, having been compressed by a factor of between 5 and 16downstream of the screws 16 and 18, rises through the outlet line 34 viathe riser pipe 36, is blown directly onto the temperature sensor 38.

The air, which still partially carries oil particles, is then conductedvia the holder 40 into the air deoiling element 42 and, if thecorresponding minimum pressure is attained, passes into the air outletline 51.

The oil 22 situated in the housing 20 is kept at operating temperaturevia the oil filter 62 and possibly via the heat exchanger 74.

If no cooling is necessary, the heat exchanger 74 is not used and isalso not activated.

The corresponding activation is performed by means of the thermostatvalve 66. After purification in the oil filter 62, oil is fed via theline 68 to the screw 18 or to the screw 16, and also to the bearing 70.The screw 16 or the screw 18 is supplied with oil 22 via the return line52, 58, and the purification of the oil 22 takes place here in the airdeoiling element 42.

By means of the electric motor (not shown in any more detail), whichtransmits its torque via the shaft 14 to the screw 16, which in turnmeshes with the screw 18, the screws 16 and 18 of the screw compressor10 are driven.

By means of the relief valve 80 (not shown in any more detail), it isensured that the high pressure that prevails for example at the outletside of the screws 16, 18 in the operational state cannot be enclosed inthe region of the feed line 32, and that, instead, in particular duringthe start-up of the compressor, there is always a low inlet pressure, inparticular atmospheric pressure, prevailing in the region of the feedline 32. Otherwise, upon a start-up of the compressor, a very highpressure would initially be generated at the outlet side of the screws16 and 18, which would overload the drive motor.

FIG. 2 shows, in a perspective view, the housing cover 20 a of the screwcompressor 10 as shown in FIG. 1.

The housing cover 20 a has an outlet which is adjoined by the air outletpipe 34.

Here, the air outlet pipe 34 has an attachment piece 34 a, by means ofwhich the air outlet pipe 34 is connected to the housing cover 20 a.

The air outlet pipe 34 furthermore has a riser line 36.

Here, the riser line 36 is of conically widened form, specifically inthe end-side region 36 a.

The air outlet pipe 34 furthermore has an oil return opening 100 in theregion of its attachment piece 34 a.

Here, the oil return opening 100 is formed as a bore.

The oil return opening 100 connects the interior of the air outlet pipe34 to the oil sump 22 a.

By means of the conical widening and the oil return opening 100, the airoutlet pipe 34 has, altogether, an oil separator which serves for theinitial oil separation even before the air compressed by the screwcompressor 10 is conducted through the oil separator.

Here, the oil separation occurs in that, owing to the conical wideningand the reduction of the flow speed that is also achieved as a result inthis region, oil particles situated in the air stream can fall backagain owing to the action of gravitational force, can precipitate on thewalls in the interior of the air outlet pipe 34, and can then flow backthrough the oil return opening 100 into the oil sump 22 a.

FIG. 3 shows a perspective sectional drawing through the air outlet pipeas per FIG. 2.

LIST OF REFERENCE DESIGNATIONS

-   10 Screw compressor-   12 Fastening flange-   14 Input shaft-   16 Screws-   18 Screws-   20 Housing-   20 a Housing cover-   22 a Oil sump-   22 Oil-   24 Inlet connector-   26 Air filter-   28 Air inlet-   30 Valve insert-   32 Air feed channel-   34 Air outlet pipe-   34 a Attachment piece-   36 Riser line-   36 a End-side region-   38 Temperature sensor-   40 Holder for an air deoiling element-   42 Air deoiling element-   44 Filter screen or known filter or oil separation devices-   46 Air outlet opening-   48 Check valve-   50 Minimum pressure valve-   51 Air outlet-   52 Riser line-   54 Filter and check valve-   56 Nozzle-   58 Oil return line-   59 Oil drain screw-   60 Attachment piece-   60 a Outer ring-   60 b Inner ring-   62 Oil filter-   64 Oil filter inlet channel-   66 Thermostat valve-   68 Return line-   70 Bearing-   72 Nozzle-   76 Safety valve-   78 Bypass line-   80 Relief valve-   82 Oil level sensor-   100 Oil return opening

1-7. (canceled)
 8. A screw compressor for a utility vehicle, comprising:a housing cover in which screws of the screw compressor are arranged;and an air outlet pipe which is arranged at an outlet side of thehousing cover and includes a riser line, wherein the air outlet pipe hasat least one oil separator.
 9. The screw compressor as claimed in claim8, wherein the oil separator comprises an oil return opening.
 10. Thescrew compressor as claimed in claim 9, wherein the oil return openingconnects an interior of the air outlet pipe to the oil sump.
 11. Thescrew compressor as claimed in claim 10, wherein the air outlet pipe hasan attachment piece by which the air outlet pipe is connected to thehousing cover, and the oil return opening is arranged in a region of theattachment piece or adjacent to the attachment piece.
 12. The screwcompressor as claimed in claim 9, wherein the oil return opening is abore.
 13. The screw compressor as claimed in claim 10, wherein the airoutlet pipe is at least partially of conical form.
 14. The screwcompressor as claimed in claim 13, wherein the riser line is of conicalform at an end side.